This invention relates to a pneumatic tire, and more particularly to a pneumatic tire whose belt construction is improved for general purpose, particularly for passenger cars.
In belt constructions of conventional tires of this kind, at least two belt layers as reinforcing elements, so-called "intersecting strips" are used whose cords intersect at acute angles within 15.degree.-25.degree. with respect to an equatorial plane of a tire.
Such a construction is intended to maintain a toroidal configuration of a radial carcass and to ensure a hoop effect for obtaining relatively flat tread surfaces and a shearing rigidity for suitably resisting to traverse forces occurring when the tire is cornering.
With such a belt construction, however, great tensile forces would occur along circumferences of the tire to expand diameters of the belt by actions of inner pressure filled in the tire, a load acting upon the tire and centrifugal forces particularly at high speeds.
In the above belt construction, as the cords of adjacent strips intersect with each other at acute angles of 15.degree.-25.degree. with respect to the equatorial plane, great shearing strains would occur between the strips at belt ends in radial sections due to the expansion of belt diameters. In an extreme case, the shearing strains may result in failure of the tire.
In order to avoid the disadvantage, it has been proposed to arrange additional reinforcing layers whose organic fiber cords or steel cords are arranged in parallel with each other along circumferences to cover belt ends of the intersecting strips in order to mitigate the expansion of the belt diameters due to tension. Such additional reinforcing layers are referred to as caps or layers.
In case of the additional reinforcing layers such as caps or layers, textile cords are mainly used for small type pneumatic tires for passenger cars so that maneuverability and durability to certain extent are accomplished. However, manufacturing cost is unavoidably increased due to an increase of members owing to the additional reinforcing layers, and the obtained durability is not necessarily sufficient.